This week's EYE ON NPI is locked in and latched on - it's CIT Relay and Switch's L115F2 Series Latching 50 A Relays, (https://www.digikey.com/en/product-highlight/c/cit/l115f2-series-latching-50-a-relays) a great way to control high voltage and currents, at a great price, and with the benefit of a latching control system so you don't need nearly as much current when activating as standard relays.

We've covered relays a few times on EYE ON NPI (https://blog.adafruit.com/2023/08/03/eye-on-npi-sensata-crydoms-series-1-ac-panel-mount-solid-state-relays-eyeonnpi-digikey-sensata-digikey-adafruit/) there's thousands of different types stocked at DigiKey, for every kind of configuration and power usage. We've even seen solid state relays (https://blog.adafruit.com/2021/01/07/eye-on-npi-te-ssrmp-series-solid-state-relays-eyeonnpi-digikey-teconnectivity-digikey/) that don't have a mechanical component. But, if you're designing something that isn't meant to switch more than 10,000 times in its lifetime, you can keep your costs low by sticking to the tried and true mechanical relay.

The only thing you might like is the upgrade of a Latching-type relay such as the L115F2 series (https://www.digikey.com/short/372fdpvv). Most relays (https://www.digikey.com/en/products/filter/power-relays-over-2-amps/188?s=N4IgjCBcoLQdIDGUBmBDANgZwKYBoQB7KAbRACYAWSgThAF0BfRg80kAJxwzQE8HGQA) are simple on-off types, when you put current through the electromagnet, it attracts the relay contacts to switch from the Normally-Closed side to Normally-Open making the circuit. The moment the current is removed, the electromagnet turns off, and the relay switches back off. That means, you have to keep that current going for as long as you want the circuit to close. For some relays, that can be quite a bit of power: it's not unusual to need up to 200mA at 5V.

If you're running on battery power, or if you want to keep your power supply budget from getting sucked up, you can swap to a latching relay. These have a 'bi-directional' electromagnet, and a plastic latching system so when you put current through one way, it will turn on and stay on. To turn off the relay, swap the polarity of the electromagnet so current goes the other way: that will unlatch the relay and turn it off. The mechanical construction is a little more expensive than a standard relay, and you'll need an H-bridge (https://en.wikipedia.org/wiki/H-bridge) to control the electromagnet, but you only need current for that short pulse.

The CIT Relay and Switch's L115F2 Series (https://www.digikey.com/en/product-highlight/c/cit/l115f2-series-latching-50-a-relays) are available in a range of configurations: with coil rated voltages of 5/12/24/48V, so you can use with whatever your native power system is. In both SPST and SPDT contacts, and either 30A, 40A or 50A rated current. There's also two size versions, the slim one still has the spade contacts on the top but they stick out rather than being sunken in the relay body..

If you want a powerful, low cost, low power solution to switching some high voltage/currents around your next product - check out the CIT Relay and Switch's L115F2 Series Latching 50 A Relays (https://www.digikey.com/en/product-highlight/c/cit/l115f2-series-latching-50-a-relays) available at DigiKey! We think Latching relays are a great way to reduce heat and power, with standard relay footprints. Order today and click-clack, within a few moments DigiKey will pack and ship your order so you can latch away into the sunset by tomorrow afternoon.

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